Radioactivity Flashcards
Atomic number
Number of protons in an atom
Mass number
Number of protons and neutrons in an atom
Isotope
Atoms of the same element that have a equal number of protons but a different number of neutrons
Radioactive decay
Some atomic nuclei are unstable and radioactive (imbalance of protons/neutrons)
The nuclei emits radiation to become more stable (a particle or wave) randomly
Alpha particles (α)
Same as a helium nucleus (2 neutrons 2 protons), 2+ charge
Speed: Slow
Ionising ability: High
Penetrating power: Low, stopped by paper
Range in air: a few cm
Beta particles (β)
Same as a high energy electron (0 mass), 1- charge
Speed: Medium
Ionising ability: Medium
Penetrating power: Medium, stopped by aluminum sheet
Range in air: ~1m
Gamma particles (γ)
Electromagnetic wave (0 mass), 0 charge
Speed: 3 x 10^8 m/s (speed of light)
Ionising ability: Low
Penetrating power: High, partially stopped by thick lead
Range in air: infinite
Ionising ability
The capacity of radiation to remove electrons from atoms
GM tube
Geiger-Muller tube: measures count rate of radiation
Sources of background radiation
Rocks (radon gas), cosmic rays, food
Becquerel
Bq = 1 nucleus in a source decaying in per second
Activity
The rate at which unstable nuclei decay
The activity of a radioactive source decreases with time
Count rate
The rate at which radioactive emissions are detected
Half life
The time it takes for the number of nuclei in a sample of radioactive isotopes to half
number of half lifes = log2(initial no. of nuclei/no. of nuclei left)
Smoke detectors
Alpha particles (blocked by smoke)
Measuring thickness of materials
Beta particles (can be partially absorbed and affected by thickness)
Radiotherapy/cancer treatment
Gamma radiation (high penetrating power)
Sterilisation
Gamma radiation (high penetrating power to clean all sides/without removing packaging)
Contamination definition
When an object becomes radioactive due to exposure to a source of radiation
Radiation cannot be blocked once an object is contaminated
Greater risk in sources with longer half-lives (remains radioactive for longer
Irradiation definition
When an object is exposed to a source of radiation but does not become radioactive
Prevention: Lead shielding etc.
Greater risk in sources with shorter half-lives (high activity and high rate of radioactive emissions)
Dangers of ionising radiation
Damage to living cells and tissues
Can cause mutations which lead to cancers
How to reduce risks of ionising radiation
Lead container
Wearing gloves and using tongs to handle radioactive materials
Wearing protective clothing
Stay in different room e.g. during Xrays
